Digital lighting technologies, i.e. illumination based on semiconductor light sources, such as light-emitting diodes (LEDs), offer a viable alternative to traditional fluorescent, HID, and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, durability, lower operating costs, and many others. Recent advances in LED technology have provided efficient and robust full-spectrum lighting sources that enable a variety of lighting effects in many applications. Some of the fixtures embodying these sources feature a lighting module, including one or more LEDs capable of producing different colors, e.g. red, green, and blue, as well as a processor for independently controlling the output of the LEDs in order to generate a variety of colors and color-changing lighting effects.
Coordinated lighting displays can be created using addressable LED-based lighting units. An “addressable” LED-based lighting unit has a unique identifier, or address (e.g., a serial number), allowing commands or data to be sent specifically to it. Therefore, addressable LED-based lighting units in a group of LED-based lighting units can be individually controlled by sending commands to the appropriate address. If the relative positions of the addressable LED-based lighting units are known, coordinated displays can be created. Some general examples of LED-based lighting units similar to those that are described in this application may be found, for example, in U.S. Pat. Nos. 6,016,038 and 6,211,626.
FIG. 1 illustrates an example of such a lighting system employing addressable LED-based lighting units. Referring to FIG. 1, a group 100 of addressable LED-based lighting units includes four addressable LED-based lighting units, 102a-102d. The four LED-based lighting units can be coordinated to produce a display in which the four colors red, green, blue, and yellow appear from left to right. In particular, addressable LED-based lighting unit 102a can be controlled, by sending a command to its unique address, to turn on red. Addressable LED-based lighting unit 102b can be controlled, by sending a command to its unique address, to turn on green. Similarly, addressable LED-based lighting units 102c and 102d can be controlled to display blue and yellow, respectively, thus completing the desired display of the four colors red, green, blue, and yellow from left to right.
Yet, to achieve the accurate coordination of the addressable LED-based lighting units 102a-102d, it is necessary to know their relative positions. The LED-based lighting units 102a-102d cannot accurately be controlled to display the colors red, green, blue, and yellow in order from left to right if it is not known in what order the lighting units are arranged. As an example, the color blue cannot be accurately made to appear at the position third from left unless it is known which LED-based lighting unit (in this case, 102c) is positioned third from left, and therefore to which address the command to “TURN ON BLUE” should be sent.
One conventional technique for determining the relative positions of addressable LED-based lighting units in a group of addressable LED-based lighting units is by pre-arranging, or positioning, the lighting units in order of their addresses. Referring again to FIG. 1, the address of each of the LED-based lighting units 102a-102d (e.g., 102b) is generally assigned to that lighting unit before it is installed, i.e., grouped with the remaining lighting units (e.g., 102a, 102c, and 102d). The address can be assigned by the manufacturer when the LED-based lighting unit is made. A group of LED-based lighting units (e.g., 102a-102d) is then packaged and sent to a customer with an indication of the order in which the lighting units should be arranged, in the order of their addresses. Alternatively, a manufacturer may package and send to a customer LED-based lighting units lacking addresses, and the customer can then set the address of the unit(s) prior to installation by connecting each unit to a programming device.
A second conventional scheme for determining the relative positions of the LED-based lighting units 102a-102d involves manually identifying the position of an LED-based lighting unit after the LED-based lighting units have been arranged. Referring again to FIG. 1, the LED-based lighting units 102a-102d are installed without knowledge of the order of the addresses of the lighting units. Then, a command is sent in turn to each of the addresses of the LED-based lighting units 102a-102d. A person watches which one of the LED-based lighting units 102a-102d turns on when a particular address is sent a command, and records the address and the relative position of that LED-based lighting unit. Typically, for large installations involving lots of LED-based lighting units, multiple people are needed to complete the process. One person controls the sending of commands to each of the possible addresses of LED-based lighting units 102a-102d, and a second person is positioned to watch all the LED-based lighting units to determine which unit turns on. In large system implementations of several LED-based lighting units (e.g., disposed on a building or other architectural structure), the second person may be positioned far away from the LED-based lighting units, such as across the street, resulting in an inconvenient and time-consuming process.